BROCKTON -- The state Supreme Judicial Court issued two rulings Thursday that could determine whether a power plant is built in Brockton.

In one decision, the court supported a decision by the state Energy Facilities Siting Board to approve a proposal for a 350-megawatt power plant on Oak Hill Way. The court ruled that the siting board's approval of the plant should stand.

But in a second ruling, the court ruled the plant would have to use waste-water -- not drinking water -- from the city's system to cool the plant, as originally proposed to the siting board. The city had denied the plant access to its waste-water system, prompting Advance Power to revise its application to use drinking water. When that change was denied, Advance Power appealed to the court.

In denying the appeal, the court appeared to give power plant opponents a victory when it wrote that the board's decision on the cooling water "appears to preclude construction of the facility as currently proposed."

Opponents of the plant had appealed the siting board's ruling based on concerns over water, traffic, air quality and other environmental issues. But the court ruled that most of the opponents' arguments were without merit, including one that calls for "environmental justice."

The municipalities of Brockton and West Bridgewater, along with residents from both communities, had sought the appeal.

Officials from Advanced Power Services, which has been seeking to build the plant on the south side of Brockton for a decade, have yet to comment on the decision.